Designation D4974 − 04 (Reapproved 2016) Standard Test Method for Hot Air Thermal Shrinkage of Yarn and Cord Using a Thermal Shrinkage Oven1 This standard is issued under the fixed designation D4974;[.]
Designation: D4974 − 04 (Reapproved 2016) Standard Test Method for Hot Air Thermal Shrinkage of Yarn and Cord Using a Thermal Shrinkage Oven1 This standard is issued under the fixed designation D4974; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision A number in parentheses indicates the year of last reapproval A superscript epsilon (´) indicates an editorial change since the last revision or reapproval D1776 Practice for Conditioning and Testing Textiles D6477 Terminology Relating to Tire Cord, Bead Wire, Hose Reinforcing Wire, and Fabrics Scope 1.1 This test method covers the measurement of shrinkage of yarns and cords when exposed in a thermal shrinkage oven 1.2 This test method is applicable to yarns and cords made of nylon, polyester, and other polymers not detrimentally affected by the temperature used and with linear densities in the range from 20 to 700 tex (180 to 6300 denier) 1.2.1 Yarns or cords for testing may be taken from yarn or cord packages or from fabrics Terminology 3.1 Definitions: 3.2 For definitions of terms relating to tire cord, bead wire, hose wire, and tire cord fabrics, refer to Terminology D6477 3.2.1 The following terms are relevant to this standard: greige cord, in tire cords, standard atmosphere for testing textiles, thermal shrinkage, tire cord 1.3 This test method shows values in both SI and inchpound units SI is the technically correct name for the system of units known as the International System of Units Inchpound units is the technically correct name for the customary units used in the United States The values stated in either acceptable metric units or other units shall be regarded separately as standard The values expressed in each system may not be exact equivalents; therefore, each system must be used independently of each other, without combining values in any way Referee decisions are to use SI units 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use Specific hazard statements are given in Section 3.3 For definitions of other terms related to textiles, refer to Terminology D123 3.3.1 The following terms are relevant to this standard: yarn Summary of Test Method 4.1 A relaxed, conditioned specimen of yarn or cord is subjected to dry heat for a specified time while under a specified tension The percent shrinkage is read directly from a scale or display on the instrument while the specimen is still under tension and exposed to heat Significance and Use 5.1 This test method may be used for the acceptance testing of commercial shipments of yarns and cords Caution is advised because yarn and cord may contract in length over a period of time due to room temperature retraction Thermal shrinkage values are reduced proportionately by the amount of room temperature retraction Referenced Documents 2.1 ASTM Standards:2 D123 Terminology Relating to Textiles D885 Test Methods for Tire Cords, Tire Cord Fabrics, and Industrial Filament Yarns Made from Manufactured Organic-Base Fibers NOTE 1—Experience, especially with nylon, shows that yarn retraction, which may be observed directly as shortening of length (or indirectly as denier increase), will occur in unrestrained yarn or cord that is not at equilibrium (equilibrium in this case being defined as essentially zero thermal shrinkage yarn or fully relaxed yarn) Normally, retractive forces are present in most wound packages of yarn and cord; thus, unrestrained yarn near the surface is likely, with time, to undergo some retraction After retraction, such yarns exhibit lower thermal shrinkage values than yarn or cord deeper within the package The opposite condition of yarn on the surface exists with yarn or cord wound against or near a rigid package core, such as a metal or hardwood wind-up spool Such core yarn or cord cannot move against this restraint, and thus, will exhibit thermal shrinkage values even several weeks later near to those which were measured This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility of Subcommittee D13.19 on Industrial Fibers and Metallic Reinforcements Current edition approved July 1, 2016 Published August 2016 Originally approved in 1999 Last previous edition approved in 2011 as D4974–04(2011) DOI: 10.1520/D4974-04R16 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 United States D4974 − 04 (2016) bias or determine the proper set point to give the specified specimen temperature immediately from the surface of the freshly wound package Elevated humidity will accelerate retraction of unrestrained yarn, but moisture content in itself will have little influence on thermal shrinkage Exposure of untensioned skeins of yarn or cord to 95 to 100 % relative humidity at room temperature for two days and reconditioning under standard laboratory conditions will cause most of the room temperature retraction that is possible within a sample to occur 6.3 The degree of room temperature length retraction, (for example, that which occurs in unrestrained skeins of yarn over time in the testing laboratory), of the laboratory sample or specimen affects the measurement of thermal shrinkage Unrelaxed nylon, for example, shrinks much more than relaxed nylon The amount of relaxation (retraction) occurring prior to testing of thermal shrinkage can affect the result 5.1.1 In case of differences of practical significance in reported test results from two or more laboratories conduct comparative tests to determine if there is a statistical bias between them Competent statistical assistance is recommended for the investigation of bias As a minimum, the parties should take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type in question The test specimens then should be assigned randomly in equal numbers to each laboratory for testing The average results from the two laboratories should be compared using Student’s t-test for unpaired data and a probability level chosen by the parties before the testing is begun If a bias is found, either its cause must be found and corrected, or future test results must be adjusted in consideration of the known bias 6.4 Frictional forces against the pulley/indicator assembly cause measurement errors Ensure that the indicator needle does not rub against the scale Maintain the pulley bearings in good condition The pulley wheel must be centered in the bearings A force of 10 mN or less, applied to the tip of the indicator needle, should cause pulley rotation when the tester is in proper operating condition 6.5 Thermal shrinkage increases as the exposure time increases Check the exposure time with a stopwatch Some thermal oven models have a timer installed Compare this timer to a stopwatch and calibrate as necessary 5.2 Thermal shrinkage of nylon, polyester, and other fibers is related to the polymer of origin and its manipulation in processing Thermal shrinkage measurement can be used to control product uniformity 6.6 Center the threadline between the heating plates of the oven to obtain a correct measurement 6.7 Specimens that are spun, textured, or crimped (as those removed from a fabric) may allow filaments to come in contact with interior surfaces of the thermal shrinkage oven Such physical contact will cause inaccurate readings of thermal shrinkage 5.3 The level of thermal shrinkage is critical in the user’s subsequent operations For example it can affect the drumset (original length of cord) required in tire building to produce a finished, final tire of a particular size 6.8 Yarn or cords that are sufficiently sticky or tacky to prevent their free release from the pulley surface as it rotates will cause inaccurate readings of thermal shrinkage 5.4 Thermal shrinkage is critical to final shape and size of fiber reinforced articles For example, thermal shrinkage affects final size of V-belts and their ability to maintain tension while running Apparatus 5.5 This test method is similar to the procedures of Methods D885 for the determination of thermal shrinkage of yarns and cords Shrinkage is measured while the specimen is within an oven and tensioned as specified in Methods D885;D885 however, there are enough vagaries among different units of apparatus for measurement of thermal shrinkage that numerical equivalence between units of different design should not be assumed, even under the same nominal conditions 7.1 Thermal Shrinkage Oven3, consisting of a specimen heating cavity capable of heating up to 250°C (480°F), a means of accurately controlling the temperature of the cavity 2°C (6 4°F), and a means for measuring and displaying the amount of specimen shrinkage to the nearest 0.1 % Fig shows the principle of operation of commercial thermal shrinkage ovens 7.2 Stopwatch or Timer Interferences 7.3 Clip-On Masses 6.1 An effective draft shield on the thermal oven is critical Because the chamber in which the specimen is heated is open on three sides, air drafts can effectively shorten the length of specimen experiencing the prescribed temperature environment Results obtained without a shield generally are lower than with a shield 7.4 Draft Shield, if the oven does not have one provided Safety Hazards 8.1 The oven portion of the tester can reach temperatures over 200°C (390° F) Do not touch the oven 8.2 Do not leave oven unattended if a specimen is installed 6.2 The accurate control of temperature at any prescribed setting is of utmost importance Bias between the set point temperature and the temperature that the specimen sees is a major cause of instrument bias The temperature that the specimen sees may be checked by attaching a small calibrated thermocouple to a piece of cord and suspending it in the specimen position such that the tip of the thermocouple is in the center of the oven cavity The thermocouple must not touch the oven walls Either correct any set point/sample temperature Sampling and Test Specimens 9.1 Primary Sampling Unit—Consider shipping containers of cords or rolls of fabric to be the primary sampling unit, as applicable Commercial thermal shrinkage ovens are available Clip-on masses also are available from the manufacturer D4974 − 04 (2016) FIG Principle of Operation of a Thermal Shrinkage Oven handling damage is available after conditioning (see 10.1) If the applicable material specification or other agreement between the purchaser and the supplier specifies testing more than one specimen per laboratory sampling unit, an additional two specimens above the number to be tested should be taken from the laboratory sampling unit and conditioned 9.2 Laboratory Sampling Unit—As a laboratory sampling unit for acceptance testing, take material randomly from the primary sampling unit as follows: 9.2.1 For cords, take spools or packages per carton using the applicable procedure in Practice D2258 9.2.2 For fabric, take from rolls at least one full-width piece of fabric that is at least m (1 yd) along the selvage (machine direction), after first discarding all fabric from the outside of the roll that contains creases, fold marks, disturbed weave, or contamination by foreign material 10 Conditioning Specimens and Preparation for Testing 10.1 Conditioning: 10.1.1 Condition specimens as relaxed skeins or segments of untensioned fabric as directed in Practice D1776 using the atmosphere specified for industrial yarns (see Section 3) Ensure that no change in yarn/cord twist occurs while carrying out this procedure 10.1.2 Condition and relax yarn and greige cord specimens 12 to 28 h 10.1.3 Condition and relax adhesive-treated cord samples 16 to 28 h, unless immediate testing (5 to 20 after processing) is agreed upon between the buyer and the supplier Immediate testing must be reported as an exception to this method (see Section 12) 9.3 Test Specimens: 9.3.1 For yarns and cords, strip at least 15 m (16 yd) from the outside of each package in the laboratory sampling unit Inspect the outside of the package after stripping off the yarn If there is visible damage, continue to strip off units of 15 m (16 yd) and reinspect until there is no visible damage Take one specimen, 600 mm (24 in.) long, from each package in the laboratory sampling unit Discard and replace specimens that are visibly damaged 9.3.2 For fabrics, remove a minimum of three lengths of warp yarn or cord 600 mm (24 in.) long from each swatch in the laboratory sampling unit, with the specimens being taken at least 75 mm (3 in.) from the selvage of the swatch For fabrics other than tire cord fabric, such as square-woven tire fabrics, also take from each swatch in the laboratory sampling unit a minimum of three lengths of filling yarn or cord 600 mm (24 in.) long after discarding those portions within 75 mm (3 in.) of the selvage of the swatch In all cases, take warp specimens that are free of filling material and filling specimens that are free of warp material 9.3.2.1 Instructions on the number of test specimens in 9.3.2 assume that a single valid thermal shrinkage result will adequately characterize the thermal shrinkage of the laboratory sampling unit from which the specimens are taken The extra two specimens are taken to assure that a specimen free of 10.2 Preparation for Testing: 10.2.1 With the draft shield in place, preheat the oven until the chamber has attained the specified temperature for a minimum of 10.2.2 Test in standard atmosphere for testing industrial yarns (see Section 3) 10.2.3 Adjust the oven temperature controller set point to give a specimen temperature of 177 °C (350 4° F) (See 6.2) 10.2.4 One may consult with the instrument vendor if calibration of the oven temperature is suspected to be in error 11 Procedure 11.1 Test Conditions (Table 1): D4974 − 04 (2016) TABLE Test Conditions Temperature 177 ± 2°C (350 ± 4°F) indicator to a shrinkage level in 11.4 sufficient to prevent the indicator from going below zero Record positive shrinkage as the interval between the lowest and highest reading of the indicator during the test of that specimen Note for the report (Section 12) the percent change in length due to crimp relaxation in the tester Time, s Specimen with Linear Specimen with Linear Mass up to 400 tex Mass Greater than (3600 denier) 400 tex (3600 denier) 5.0 ± 1.0 mN/tex 120 ± 10 240 ± 10 (or 0.05 ± 0.01 gf/den) Tension Load 11.7 Lower the draft shield immediately after introducing the specimen 11.8 Start the timer at the moment the draft shield is lowered 11.1.1 For yarns or cords possessing low levels of shrinkage force, a tension loading of 1.0 0.2 mN/tex (0.010 0.002 gf/den) may be used Use of this lower tension load should be noted in the report 11.9 At the end of 120 10 s (240 10 s for specimens equal to or greater than 400 tex or 3600 denier), read the percent shrinkage as indicated on the instrument output to the nearest 0.1 % 11.2 Install one end of the specimen in the fixed clamp 11.10 Remove and discard the specimen 11.3 Bring the other end of the specimen over the pulley 12 Report 11.4 Set the indicator to zero and hold it on zero while performing the next step 12.1 State that the specimens have been tested as directed in Test Method D4974 Describe the material(s) or product(s) tested and the method of sampling used Report the following information: 12.1.1 Individual thermal shrinkage results as indicated on the instrument output to the nearest tenth of a unit 12.1.2 Mass, in g, used to apply tension force 12.1.3 Measurements as “immediate testing” if not conditioned for standard period (see 10.1.2 and 10.1.3) 12.1.4 Measurements as “package testing” if specimens are not removed from package and relaxed prior to testing 12.1.5 “Percent length increase prior to shrinkage” if such occurred during testing (see Note 3) 11.5 Attach a clip-on mass to the unclamped end of the specimen so that twist is not lost Use a mass that creates a tension load as specified in 11.1 Table shows the total mass needed to effect such tensions for typical yarns and cords NOTE 2—If the specimen is likely to untwist in the portion below the pulley, attach a toothpick or the equivalent (approximately 7.5 cm long) to the mass or clamp, perpendicular to the vertical threadline, so it will bear against the instrument case and prevent rotation of the mass 11.6 Load specimen(s) into the oven The specimen is centered automatically in the oven NOTE 3—In the case of highly-crimped yarns, typically those removed from tightly woven fabric, the initial dimensional change that occurs is usually growth, that is, an immediate elongating of the specimen as the specimen loses crimp and straightens If the instrument allows, set the 13 Precision and Bias 13.1 Interlaboratory Test Data—An interlaboratory test was conducted in 2000 using commercially available testers from Lawson-Hemphill, Lenzing, and Testrite Six tire cord materials were included in the study, varying in polymeric structure (nylon and polyester), form (yarn, greige cord, and dipped cord), and linear density The type of materials chosen and their processing conditions produced an intentional thermal shrinkage among the specimens from less than % to greater than % Thirteen laboratories participated in the study Three of the laboratories used two instruments for a total of sixteen instruments In each laboratory two operators made triplicate shrinkage measurements on each of four test occasions Variance components were computed for individual thermal shrinkage determinations and are summarized in Table TABLE Tensioning MassesA,B A Single-Strand Yarns d Tex Denier 235 210 940 840 1100 1000 1170 1050 1400 1260 1440 1300 1870 1680 2100 1890 B Multiple Strands or Cords of Multiple Strands Construction 940 × 840 × 1100 × 1000 × 1400 × 1260 × 1440 × 1300 × 1870 × 1680 × 2100 × 1890 × Tensioning Mass, g 10 42 50 53 63 65 84 95 Tensioning Mass, g 84 100 126 130 168 189 13.2 Precision—Repeatability and reproducibility deal with the variability of test results obtained under specified laboratory conditions Repeatability concerns the variability between independent test results obtained within a single laboratory in the shortest practical period Those results are obtained by a single operator with a specific set of test apparatus using test specimens (or test units) taken at random from a single quantity of homogeneous material obtained or prepared for the interlaboratory study (ILS) Reproducibility deals with the variability between single test results obtained in different laboratories, each of which has applied the test method to test specimens (or test units) taken at random from a single quantity of homogeneous material obtained or prepared for the ILS A For yarns or cords not shown in Table 2, calculate clip-on mass required by multiplying total d Tex of specimen by 0.50 mN or total denier by 0.05 gf (for specimens expected to have low shrinkage tensions, the factors are are 0.090 mN and 0.01 gf, respectively) B If yarns or cords outside the linear density specified in this test method are tested on this type equipment, it may be necessary to use more mass in tensioning light yarns (to ensure sufficient friction to accurately move the pulley) or less mass in tensioning very heavy yarns or cords (to prevent overstressing of the pulley bearings) In such an event, show, in addition to the mass in grams in 12.1.2, the words modified procedure, immediately followed in parentheses by the calculated tension per unit of linear density, such as millinewtons per denier or grams per denier For example, testing of a 10 000-denier cord with 100 g of tensioning mass will be reported in 12.1.2 as “100-g modified procedure (0.01 gf/denier).” Polyester Yarn 1400 dtex Nylon Yarn 930 dtex Nylon Yarn 1880 dtex Polyester Cord 1400/ 1/2 Nylon Cord 930/1/2 Nylon Cord 1800/1/2 Material 0.043665 0.40272 0.167416 0.004404 0.580907 0.126382 7.6 6.5 0.94 7.7 5.4 Variance Lab 5.2 Average Shrinkage -0.00434 0.006947 0.002372 0.009564 0.000046 0.015556 0.001816 0.000544 0.001638 0.001451 -0.00011 -0.00076 Variance Operator 0.030175 0.010189 0.010809 0.004993 0.002657 0.003951 Variance Occasion 0.016896 0.018177 0.019147 0.014463 0.002752 0.010685 Variance Determination 0.625454 0.162239 0.436686 0.197887 0.009749 0.073097 Total Variance TABLE Interlaboratory Study Variance Components Variance Instrument 0.044547 0.035857 0.033966 0.030471 0.005345 0.029432 Within-Lab Variance 0.13 0.13 0.14 0.12 0.05 0.10 s (repeatability) 0.21 0.19 0.18 0.17 0.07 0.17 s (within-lab) 0.79 0.40 0.66 0.44 0.10 0.27 s (reproducibility) D4974 − 04 (2016) D4974 − 04 (2016) the single operator case (“repeatability”), within-laboratory case, and between-laboratory case (“reproducibility”) Two values or averages of observed values are considered significantly different at the 95 % probability level if the difference between them exceeds the appropriate critical difference in the table Method repeatability is defined as the “maximum difference” that can “reasonably” be expected between two test results obtained on the same material when the test results are obtained in the same laboratory Repeatability standard deviation is taken to be the square root of the “determination” variance component, and represents within-operator precision Method reproducibility is defined as the “maximum difference” that can “reasonably” be expected between two test results obtained on the same material when the test results are obtained from different laboratories The total, or reproducibility, standard deviation, is formed by taking the square root of the sum of intra- and inter-laboratory variance components The values in Table show maximum critical differences for single determinations specified averages of determinations for 13.3 Bias—The procedure in this test method produces a test value that can be defined only in terms of a test method There is no independent referee method by which bias may be determined This test method has no known bias 14 Keywords 14.1 shrinkage; thermal; tire cord D4974 − 04 (2016) TABLE Maximum Critical Differences Material Polyester Yarn 1400 dtex Nylon Yarn 930 dtex Nylon Yarn 1880 dtex Polyester Cord 1400/1/2 Nylon Cord 930/1/2 Nylon Cord 1880/1/2 Number of Observations 16 16 16 16 16 16 Single Operator Precision 0.287 0.203 0.143 0.101 0.072 0.384 0.271 0.192 0.136 0.096 0.333 0.236 0.167 0.118 0.083 0.145 0.103 0.073 0.051 0.036 0.360 0.255 0.180 0.127 0.090 0.374 0.264 0.187 0.132 0.093 Within-Laboratory Precision 0.476 0.336 0.238 0.168 0.119 0.511 0.361 0.255 0.181 0.128 0.484 0.342 0.242 0.171 0.121 0.203 0.143 0.101 0.072 0.051 0.585 0.414 0.293 0.207 0.146 0.525 0.371 0.262 0.186 0.131 Between Laboratory Precision 0.749 0.530 0.375 0.265 0.187 1.832 1.295 0.916 0.648 0.458 1.233 0.872 0.617 0.436 0.308 0.274 0.194 0.137 0.097 0.068 2.192 1.550 1.096 0.775 0.548 1.116 0.789 0.558 0.395 0.279 ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn Your 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